RAIL COUPLING FOR CONNECTING A GROUND CABLE TO A SAFETY STRIP

Abstract: The invention relates to a rail coupling for connecting a ground cable to the supply-current conductor rail of a cabinet or a box or to the output terminal of a safety strip. The rail coupling includes a body (1), a connecting bracket (3), extending therefrom and fastenable with a screw to said rail or terminal, a jaw element (6), movable by means of a clamping screw (8) and defining a space (2) in the body (1) for receiving the end of a ground cable, as well as a shroud cover (12) surrounding the coupling. A surface included in said connecting bracket (3) and adjoining said body space (2) is provided with teeth (5) piercing the insulating cover of a cable, the cable being clampable by means of said jaw element (6) against the teeth (5). The components can be made of an aluminium profile and a moment screw (8-10) can be used for securing a sufficient clamping for enabling the teeth (5) to pierce the insulating cover.

Description: Rail coupling for connecting a ground cable to a safety strip. The present invention relates to a rail coupling for connecting a ground cable to the supply-current conductor rail of a cabinet or a box or to the output terminal of a safety strip, said rail coupling comprising a body, a connecting bracket, extending therefrom and fastenable with a screw to said rail or terminal, a jaw element, movable by means of a clamping screw and defining a space in the body for receiving the end of a ground cable, as well as a shroud cover surrounding the coupling. This type of rail couplings are used for connecting insulated low-voltage ground cables to safety strips. At the moment, the only available rail coupling are those that require the stripping of an insulating cover off the end of a cable for creating a contact. Neither are the prior known couplings preferred in terms of manufacturing technique, including e. g. cast elements. Yet another drawback when using the prior art couplings is that, in order to thread the end of a cable into the coupling, the cable must either be bent or the coupling first removed from its fastening screw. An object of the invention is to provide a rail coupling of the above type, which substantially facilitates the installation work especially for the reason that the end of a cable need not be stripped off. At the same time, the other above-mentioned drawbacks can be eliminated. This object is achieved by the invention on the basis of the characterizing features set forth in the appended claims. Two exemplary embodiments of the invention will now be described with reference made to the accompanying drawings, in which fig. 1 shows a coupling of the invention in the axial direction of a cable and fig. 1A shows a moment screw in a plan view. Fig. 2 shows the same coupling in a side view; fig. 3 shows a twin coupling according to a second embodi ment of the invention in the axial direction of cables and fig. 4 shows the same coupling in a side view. In the embodiment shown in figs. 1 and 2, a coupling body 1 is made by cutting a piece of a desired length off a Cshaped aluminium profile. A connecting bracket or a connecting rail 3 is also cut off an aluminium profile having a cross-sectional shape which is shown in fig. 1. The connecting bracket is provided on one side with a serration 5 which excluded from the section extending from the body. The serrations or teeth 5 have a length which is sufficient for piercing the insulating cover of a ground cable and penetrating into the metal conductor for creating an electrical contact. The connecting bracket 3 is provided with a hole 4 for a fastening screw in view of securing the coupling to the supply-current conductor rail of a cabinet or a box or to the output terminal of a safety strip. The space defined by said body 1 further includes a jaw element 6 which is movable by a clamping screw 8 in the longitudinal direction of said screw 8, i. e. towards or away from the teeth 5. Preferably, the jaw element 6 is also provided with teeth 7 capable of piercing the insulating cover and penetrating into the conductor metal. The clamping screw 8 is designed as a moment screw by providing the screw 8 with a head 9 through the intermediary of a reducing section 10. The clamping screw 8 is tightened until the head 9 breaks off the screw 8. This makes sure that the teeth 5 and 7 have penetrated sufficiently into a cable to be connected. In order to disassemble the connection, if necessary, the end of said screw 8 is provided with a second head 11 which remains permanently in the head of the screw 8. The head 11 is preferably of such a design that it is partially more extensive than the head 9, whereby a socket wrench or spanner gripping the head 9 remains on top of the head 11 and is not able to grip said head 11 (see fig. 1A). Thus, if necessary, the screw 8 is disengageable with a standard tool capable of gripping the head 11. After the installation and in operating condition, the live coupling is surrounded by a shroud cover 12 made of a transparent plastic material. Thus, the connecting rail 3 and the jaw element 6 are made of an aluminium profile. In order to make the contact elements, i. e. the teeth 5 and 7, suitable for both copper and aluminium wires, said teeth 5 and 7 are coated with tin. The connecting rail 3 has a sufficient length between the hole 4 and the body 1 for moving said body 1 preferably over its entire length along the connecting rail 3. Thus, the body 1 can be turned completely out of the way while the end of cable is turned into position, whereafter the body 1 is pulled back along the rail 3 over the serrated section 5 and, thus, the end of a cable is retained in a space 2 defined by the jaw element 6 and the connecting rail 3. Hence, there is no need to bend the rigid cable for inserting the cable end into the coupling. The above description applies also to the embodiment shown in figs. 3 and 4. The only difference from the above is that the coupling is designed as a twin coupling by including an additional jaw element 13 between the serrated section 3,5 of the connecting rail 3 and the jaw element 6. The opposing surfaces of the additional jaw element 13 are also provided with teeth 14,15 piercing through the cable insulation and penetrating into the conductor metal. The additional jaw element 13 is capable of a free movement in the direction of the clamping screw 8. This embodiment proposes the use of two moment screws 8. It is obvious that both embodiments can be optionally provided with one or two moment screws. As shown in fig. 4, even in this case a distance between the end of the connecting rail 3 and the hole 4 is nearly twice the length of the body 1 in the direction of the rail 3. This also enables such a displacement of the body 1 that the end of a cable can be fitted therein by turning the cable without substantially bending the cable.

Claims: Claims 1. A rail coupling for connecting a ground cable to the supply-current conductor rail of a cabinet or a box or to the output terminal of a safety strip, said rail coupling comprising a body (1), a connecting bracket (3), extending therefrom and fastenable with a screw to said rail or terminal, a jaw element (6), movable by means of a clamping screw (8) and defining a space (2) in the body (1) for receiving the end of a ground cable, as well as a shroud cover (12) surrounding the coupling, c h a r a c t e r i z e d in that a surface included in said connecting bracket (3) and adjoining said space (2) is provided with teeth (5) piercing the insulating cover of a cable, the cable being clampable by means of said jaw element (6) against the teeth (5). 2. A rail coupling as set forth in claim 1, c h a r a ct e r i z e d in that the jaw element (6) is also provided with teeth (7) piercing the insulating cover of a cable. 3. A rail coupling as set forth in claim 1 or 2, c h a ra c t e r i z e d in that between the serrated section (3, 5) of the connecting bracket (3) and the jaw element (6) is an additional jaw element (13), which is capable of a free movement in the direction of the clamping screw (8) and which has one surface provided with teeth (14) opposite to the jaw element (6) and a second surface provided with teeth (15) opposite to the teeth (5) of the connecting bracket (3), thus creating a twin coupling for connecting two cables by a single coupling. 4. A rail coupling as set forth in any of claims 1-3, c h a r a c t e r i z e d in that the body (1) comprises a piece of a C-shaped profiled aluminium rod having a desired length. 5. A rail coupling as set forth in any of claims 1-4, c h a r a c t e r i z e d in that the connecting bracket (3) and the jaw element (6) are pieces cut off a profiled aluminium rod and fitted in a space defined by the body (1). 6. A rail coupling as set forth in any of claims 1-5, c h a r a c t e r i z e d in that the connecting bracket (3) comprises a rail for manipulating the body (1) therealong. 7. A rail coupling as set forth in claim 6, c h a r a ct e r i z e d in that said connecting rail (3) is provided with a fastening-screw hole (4) whose distance from the end of the connecting rail (3) is at least twice the length of the body (1) in the direction of the connecting rail (3). 8. A rail coupling as set forth in any of claims 1-7, c h a r a c t e r i z e d in that said clamping screw (8) is a moment screw, including a first screw head (9) which is connected by way of a breakable reducing section (10) with a second screw head (11) which is a permanent part of the clamping screw (8). 9. A rail coupling as set forth in claim 8, c h a r a ct e r i z e d in that, if necessary, the clamping screw (8) is disengageable with a standard tool capable of gripping said second screw head (11). 10. A rail coupling as set forth in any of claims 4-6, c h a r a c t e r i z e d in that the meshing surfaces of the connecting bracket and the C-shaped body are provided with recesses and ridges which provide a shaped locking for preventing the body ends from drawing away from each other.

Inventors: SOEDERHOLM HENRIK, SOEDERHOLM, HENRIK
Applicants: SEKKO AB OY, SOEDERHOLM HENRIK, OY SEKKO AB, SOEDERHOLM, HENRIK
Application year: 1994
Main classification: H01R4
IPC codes: H01R4